Electrophysiology Flashcards
RMP
Resting Membrane Potential
-90 mV for a motor neuron
Which region is negatively charged RELATIVE to the other?
Intracellular surface relative to extracellular surface
Resting motor neuron has a high [intracellular] of ____ and [extracellular] of _______
K+
Na+
Na/K ATPase is essential for maintaining
Resting electrochemical gradients for electrogenic cells
EMF
Electromotive Force
Tendency for ion to move in one direction or another
EMG is dependent on (2)
Na, K, Cl concentrations
Membrane permeability of the ions
RMP is set by
K concentration gradient across cell membrane
What happens if plasma K is elevated?
Concentration gradient is lowered across cell membrane
RMP is less negative
Membrane depolarizes (less K is leaving)
Larger the K concentration gradient =
Greater negativity in cell
AP can be recorded and measured as
Electric current (INa+)
If voltage-dependent gates are open then….
There’s a significant change in net ionic flux
3 general phases of AP
- Resting
- Depolarization
- Repolarization
Resting phase
Polarized
In RMP
Depolarization
Inc. permeability to Na due to opening of voltage-gated channels
Membrane becomes less negative
Threshold potential
Membrane voltage where INa+ isn’t opposed by any other forces
Towards end of depolarization, what happens?
Voltage gated K being to open to diffuse out of the cell
Repolarization
Voltage gated Na close
Voltage gated K stay open since membrane is still permeable
2 types of voltage gated Na channels
Activation (extracellular side)
Inactivation (cytoplasmic side)
Resting conformation for voltage gated Na channel
Inactivation gates open
Activation gates closed
Depolarization conformation for voltage gated Na channels
Inactivation and activation gates open
Repolarization conformation for voltage gated Na channels
Inactivation and activation gates closed
Voltage gated Na and K channels are ________ dependent for _______
Voltage and time
Activation and inactivation
Greatest % of K channels open around
60mV
Voltage gated Ca channels are _________ activating
Slow
2 types of Ca channels
L- type (long)
T- type (transient)
T-type channels
Pacemaker of SA node
Activate and inactivate over more negative Vm
L-type channels
Plateau phase of AP in vascular SM and cardiac myocytes
High threshold for activation
Threshold potential can be changed in response to
Physiological conditions
Ex: temperature, hypoxia, pH, anesthesia
Subthreshold stimuli activate _____ to allow _____ influx
Ligand gated Na channels
Na
Graded potentials are proportional in ______ to the ______
Amplitude
Stimulus strength
Graded potentials are also known as ______
Subthreshold changes in membrane potential
2 types of graded potentials
Excitatory post-synaptic potentials (EPSP)
Inhibitory post-synaptic potentials (IPSP)
To reach threshold, some graded potentials can ______ which is common in regulating communication between ______ and ______
Summate
Neurons (neuroneruonal transmission)
Motor neurons and skeletal muscle (neuromuscular)
Absolute Refractory Period
Also known as effective refractory period
Another AP can’t be initiated while Na inactivation gates are closed
Absolute refractory periods extends until
Enough voltage gated na channels are in resting conformation
Relative Refractory Period
Limited APs can be generated during the recovery phase which a strong enough stimulus
proper Na and K concentration needed for RMP is restored by
Na/K ATPase
How many APs can be fired before the [Na] and [K] prevents generating another AP
100,000 - 150,000
Common stimuli of APs are (6)
Ions Neurotransmitters Mechanical manipulation of neural tissue Electric current Electromagnetic energy Pharmacological agents
AP spread electrical activity to ______ of the plasma membrane due to migration of _____ between the ______ area and __________ regions of resting plasma membrane
Adjacent portions
Na+
Depolarizes area
Adjacent
Migration of Na induces: (3)
- Membrane depolarization of adjacent regions
- Activation of voltage gated Na channels
- AP
An AP is propagated from the _______, along the ______ via a series of _________
Initial activation site
Membrane
Na induced depolarizations
Myelin (2)
Phospholipid/cholesterol substance
Formed by Schwann cells
Myelin sheath
Prevents conductivity
AP are NOT generated where?
Within myelin
AP can only be generates in the
Nodes of Ranvier
Saltatory conduction requires less ______ than the _____
Energy
Cable-like conduction of AP in non-myelinated neurons
Repolarization always relies on
K (Potassium!)
SA node maintains
Cardiac rate and rhythm
HCN channels stand for
Hyperpolarized-activated Cyclic Nucleotide-Gated
During the depolarization phase in pacemaker potentials, ________ subsequently inactivate
T-type Ca channels
Hyperpolarization of Pacemaker potential is needed in order to
Reactivate HCN channels to allow the process to repeat
Plateau potentials regulate
Cardiomyocyte contractility
Inward positive current results in
Depolarization
Outward positive current OR inward negative current results in
Repolarization or hyperpolarization
Plateau potential steps (4)
- Na influx (depolarization)
- Transient K dependent repolarization
- Activate voltage gated Ca channels (moves in), outward K flow
- Diff. Isoform of K channel activated (repolarization)
Nociceptors
Mediate pain signal
Somatic sensory receptors
Nociceptor afferents are ______ and consist of ______ and _______ fibers
Nerve fibers relaying into CNS
Myelinated
Unmyelinated
Myelinated fibers are (3):
Medium to large diameter
Fast conducting
Relay fast pain (sharp, intense)
Type C pain afferents (4):
Small diameter
Unmyelinated
Slow conducting
Relay sensations of dull, burning pain
Local anesthetics work by
Reversible blocking AP
Local anesthetics are usually _____ at pH ____ and are _____
Weak bases
7.4
Lipid soluble
How does an anesthetic work? (4)
- Protonation due to acidic intracellular pH of neuron
- Bind to receptor site of voltage gated Na channel
- Prevents activation gate from opening
- Neuron can’t depolarize and fire AP so pain signal isn’t relayed
2 ways a synaptic transmission (AP) is relayed
- Neuroneuronal (between neurons)
2. Neuromuscular (between neurons and affector tissues)
Synaptic Transmission steps: (6)
- Voltage gated Ca channels open
- Can flows into nerve terminus
- Ca dependent signaling
- Synaptic vessicles fuse to pre-synaptic membrane (on intracellular side)
- Neurotransmitters released into synapse
- Ligand binds receptor to elicit response
Chemical synapses are ____and use _____ to relay _____
Wider
Neurotransmitters as messengers
AP between cells
Excitatory neurotransmitters
Glutamate
Aspartate
Inhibitory neurotransmitters
GABA
Glycine
Electrical synapses are not _____, whereas chemical synapses make up the _______
Common
Majority
Chemical synaptic transmitting categorized into: (2)
Ionotropic
Metabotropic
Ionotropic transmission
Uses NT to activate ligand gated channels in post-synaptic membrane
Ligand channels can be excitatory or inhibitory
Which type of chemical transmission is faster? (Ionotropic or Metabotropic)
Ionotropic transmission
Metabotropic transmission
Relies on release of NT and the activation of receptor-mediated signaling in effector tissue
Example of metabotropic transmission
Controlling heart rate via ACh activating CM2 receptors in SA node
Example of ionotropic transmission
Nicotine-cholinergic receptor in skeletal muscle (excitatory)
Synaptic fatigue occurs
After sustained stimulation of neuronal transmission
